Optical fiber reel module and winding method therefor

ABSTRACT

A optical fiber reel module including a reel having a continuous outer circumference and an optical fiber wound around the reel. The optical fiber reel module further includes an adjustable diameter between a first length and a second length and after an optical fiber is wound around the reel.

This application is a divisional of U.S. application Ser. No. 10/928,854filed on Aug. 27, 2004 and claims priority from International PCTApplication NO. PCT/JP02/03929, filed Apr. 19, 2002, the contents ofwhich are herein wholly incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to an optical fiber module andwinding method therefor, and more particularly to an optical fiber reelmodule and a winding method therefor.

2. Description of the Related Art

An optical communication system using an optical amplifier for directlyamplifying an optical signal has become general, and an EDF module isused as a basic component of such an optical amplifier having an opticalamplifying function. FIG. 1 shows an EDF module 1 in the related art. Asshown in FIG. 1, the EDF module 1 is configured by winding an Er dopedoptical fiber 4 around a metal reel 2. By adjusting the length of the Erdoped optical fiber 4, the amplification characteristic is set to arequired value. Further, normal single-mode optical fibers are splicedto the opposite ends of the Er doped optical fiber 4.

The spliced portion between the Er doped optical fiber 4 and eachsingle-mode optical fiber is protected by dropping a UV curing resin tothe spliced portion and directing UV radiation to the UV curing resin tocure the same. This process is referred to as recoating of the splicedportion. After protecting each spliced portion by this recoatingprocess, the single-mode optical fibers are also wound around the reelfor storage. In an EDF module for a wavelength division multiplexing(WDM) amplifier, uniform temperature control of an Er doped opticalfiber is performed by utilizing heat conduction of a metal reel asmeasures against the temperature dependence of amplificationcharacteristic.

The related art EDF module 1 using the metal reel 2 has such a problemthat the loss due to stress generated in winding the Er doped opticalfiber 4 is increased. Accordingly, the loss contributing to theamplification characteristic of the Er doped optical fiber 4 itselfbecomes unclear, so that the adjustment of high-precision amplificationcharacteristic is impossible. Since the Er doped optical fiber 4 is keptwound around the metal reel 2, stress is always applied to the Er dopedoptical fiber 4, causing a reduction in reliability. While another metalreel whose diameter is adjustable is used, such a metal reel iscomplicated in structure and it is therefore costly.

FIGS. 2 and 3 show another EDF module 5 in the related art as applied toan EDF module which does not require temperature control. As shown inFIG. 2, an Er doped optical fiber 4 is wound around a metal reel 6.Thereafter, the Er doped optical fiber 4 is removed as a bundle from themetal reel 6. The metal reel 6 is formed with a plurality of bundlingrecesses 8. FIG. 3 shows the EDF module 5 removed from the metal reel 6.Reference numerals 10 denote spliced portions between the Er dopedoptical fiber 4 and single-mode optical fibers 12. Reference numerals 14denote bundling tubes.

As shown in FIG. 3, the EDF module 5 is removed from the metal reel 6for use, so that the stress always applied to the Er doped optical fiber4 can be removed. However, it is necessary to use the metal reel 6having such a special shape that it has the bundling recesses 8 forbundling the Er doped optical fiber 4 as shown in FIG. 2. Accordingly,there is a possibility that the coating of the Er doped optical fiber 4may be deformed and/or damaged. Further, in adjusting the length of theEr doped optical fiber 4 or in splicing the single-mode optical fibers12 to the opposite ends of the Er doped optical fiber 4, it is necessaryto once remove the bundling tubes 14 and to bundle the Er doped opticalfiber 4, so that the operation becomes troublesome. In the case thattemperature control of the Er doped optical fiber 4 is necessary, theEDF module 5 shown in FIG. 3 must be stored into a container fortemperature control.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide arare-earth doped optical fiber module which can relieve the stressgenerated in winding a rare-earth doped optical fiber, thereby allowinghigh-precision adjustment of the amplification characteristic.

It is another object of the present invention to provide a manufacturingmethod for a rare-earth doped optical fiber module which can relieve thestress generated in winding a rare-earth doped optical fiber.

In accordance with an aspect of the present invention, there is provideda rare-earth doped optical fiber module including a resin reel havingelasticity; and a rare-earth doped optical fiber wound around the resinreel.

Preferably, the resin reel is formed of silicone rubber, fluororubber,or soft PVC. Preferably, the rare-earth doped optical fiber modulefurther includes a metal tape embedded in the resin reel so as to extendin the circumferential direction of the resin reel, the metal tape beingfabricated by twisting metal wires into the form of a net. Morepreferably, a heater and a temperature sensor are mounted on the resinreel, and the heater is in contact with the metal tape.

In accordance with another aspect of the present invention, there isprovided a manufacturing method for a rare-earth doped optical fibermodule, including the steps of setting a resin reel having elasticity ona metal reel whose diameter is changeable between a first diameter and asecond diameter larger than the first diameter; increasing the diameterof the metal reel to the second diameter to thereby increase thediameter of the resin reel; winding a rare-earth doped optical fiberaround the resin reel; decreasing the diameter of the metal reel to thefirst diameter; and removing the resin reel having the rare-earth dopedoptical fiber from the metal reel.

Preferably, the manufacturing method further includes the step ofsplicing a single-mode optical fiber to the rare-earth doped opticalfiber after decreasing the diameter of the metal reel to the firstdiameter and before removing the resin reel from the metal reel.

The above and other objects, features and advantages of the presentinvention and the manner of realizing them will become more apparent,and the invention itself will best be understood from a study of thefollowing description and appended claims with reference to the attacheddrawings showing some preferred embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partially cutaway, perspective view of an EDF module in therelated art;

FIG. 2 is a side view of a metal reel for bundling an Er doped opticalfiber in the related art;

FIG. 3 is an elevational view of another EDF module in the related artobtained after bundling the Er doped optical fiber shown in FIG. 2;

FIG. 4 is a sectional view of an EDF module according to a firstpreferred embodiment of the present invention in the condition where theEDF module is mounted on a metal reel;

FIG. 5 is a cross section taken along the line V-V in FIG. 4;

FIG. 6 is a side view of a first segment of the metal reel in thecondition where the diameter of the metal reel is increased;

FIG. 7 is a partially cutaway, perspective view of the EDF moduleaccording to the first preferred embodiment; and

FIG. 8 is a partially cutaway, perspective view of an EDF moduleaccording to a second preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 4, there is shown a sectional view of an EDF module 16according to a first preferred embodiment of the present invention inthe condition that the EDF module 16 is mounted on a metal reel 18. FIG.5 is a cross section taken along the line V-V in FIG. 4. The metal reel18 is composed of a first segment 20 having a center hole 22 and asecond segment 24 having a shaft 26 inserted in the center hole 22 ofthe first segment 20. A resin reel 28 having elasticity is mounted onthe metal reel 18. The resin reel 28 is formed of silicone rubber,fluororubber, or soft polyvinyl carbazole (PVC), for example. The resinreel 28 is fabricated by using a mold so that the outer diameter of thebottom of the resin reel 28 becomes 60 mm.

As shown in FIG. 6, the first segment 20 of the metal reel 18 iscomposed of a first semicircular reel 20 a and a second semicircularreel 20 b. A pair of pins 30 and 32 are fixed to the first semicircularreel 20 a. The second semicircular reel 20 b is connected to a bracket34. The bracket 34 is formed with a pair of elongated holes 36 and 38.The pins 30 and 32 are inserted in the elongated holes 36 and 38,respectively. Accordingly, the second semicircular reel 20 b is movablebetween a diameter decreased position where the second semicircular reel20 b is in contact with the first semicircular reel 20 a and a diameterincreased position where the second semicircular reel 20 b is spacedapart from the first semicircular reel 20 a by a predetermined distanceas shown in FIG. 6.

After mounting the resin reel 28 on the metal reel 18, the outerdiameter of the metal reel 18 is increased as shown in FIG. 6 so thatthe outer diameter of the bottom of the winding portion of the resinreel 28 is increased from 60 mm to 61 mm. In this condition, an Er dopedoptical fiber 42 is wound around the resin reel 28. Thereafter, theouter diameter of the metal reel 18 is reduced to restore the originalouter diameter (=60 mm) of the bottom of the winding portion of theresin reel 28 and to adjust the length of the Er doped optical fiber 42,thereby setting the amplification characteristic to a target value.Thereafter, single-mode optical fibers 44 are spliced to the oppositeends of the Er doped optical fiber 42, and the spliced portions arerecoated with a UV curing resin for reinforcement. Thereafter, thesingle-mode optical fibers 44 are wound around the resin reel 28 forstorage. The second segment 24 of the metal reel 18 is removed from thefirst segment 20, and the resin reel 28 is next removed from the firstsegment 20 to obtain the EDF module 16 according to the first preferredembodiment shown in FIG. 7.

In the conventional EDF module 1 shown in FIG. 1 wherein the Er dopedoptical fiber 4 is wound around the metal reel 2, a loss increase due toa winding stress to the Er doped optical fiber 4 is 0.5 to 1.5 dB. Incontrast, the EDF module 16 according to the above preferred embodimentcan obtain a stress-free condition, and the loss increase can besuppressed to 0.1 dB or less.

An EDF module for a WDM amplifier is required to suppress the influenceof temperature characteristics. FIG. 8 shows an EDF module 16′ accordingto a second preferred embodiment of the present invention which canperform temperature control. The EDF module 16′ includes a metal tape 46embedded in a resin reel 28 along the inner circumference thereof. Themetal tape 46 is fabricated by twisting metal wires into the form of anet. The embedding of the metal tape 46 in the resin reel 28 may beperformed in molding the resin reel 28. The metal tape 46 fabricated bytwisting metal wires into the form of a net has elasticity, so that theelasticity of the resin reel 28 can be maintained.

The inner circumference of the resin reel 28 is partially removed tothereby expose a part of the metal tape 46. A sheetlike heater 48 isattached to the exposed portion of the metal tape 46. Further, atemperature sensor 50 such as a resistance thermometer is attached toanother portion of the inner circumference of the resin reel 28. Thetemperature of the resin reel 28 is detected by the temperature sensor50, and the heater 48 is controlled so that the temperature of the resinreel 28 becomes 60□. The temperature of an Er doped optical fiber 42 andsingle-mode optical fibers 44 wound around the resin reel 28 can becontrolled to a uniform temperature of 60±0.5□ over the circumference ofthe resin reel 28 by the heat conduction of the metal tape 46.

The present invention is applicable similarly to a rare-earth dopedoptical fiber fabricated by doping an optical fiber with any one of theother rare-earth elements.

According to the present invention as described above, the stressgenerated in winding the Er doped optical fiber can be relieved, and theamplification characteristic can be adjusted to a target valueaccurately and stably. Further, a reduction in reliability due to thestress caused by thermal expansion of the reel, for example, can beprevented, and uniform temperature control can be easily performed.

Further, the resin reel can be simply formed by molding at a low cost.The spliced portion can also be wound on the resin reel with a givenbend radius. Since the Er doped optical fiber is wound around the resinreel, the shape of the fiber can be deformed to allow an increase indegree of freedom of mounting to an optical amplifier module.

The present invention is not limited to the details of theabove-described preferred embodiments. The scope of the invention isdefined by the appended claims and all changes and modifications as fallwithin the equivalence of the scope of the claims are therefore to beembraced by the invention.

1. An optical fiber module comprising: a reel with a continuous outercircumference and an adjustable diameter between a first length and asecond length; and an optical fiber wound around said reel.
 2. Theoptical fiber module according to claim 1, wherein said optical fiberhaving a spliced portion.
 3. The optical fiber module according to claim1, wherein said continuous outer circumference of said reel is formed ofa material selected from the group consisting of silicone rubber,fluororubber, and soft PVC.
 4. The optical fiber module according toclaim 1, wherein said reel having a metal member embedded in said reel.5. The optical fiber module according to claim 4, wherein said metalmember has an exposed portion from said reel; a heater in contact withsaid exposed portion of said metal member.
 6. The optical fiber moduleaccording to claim 4, wherein said metal member comprises a metal tapefabricated by twisting metal wires into the form of a net.
 7. Theoptical fiber module according to claim 5, further comprising atemperature sensor mounted on said reel.
 8. A reel assembly comprising:a reel with a continuous outer circumference and an adjustable diameterbetween a first length and a second length; and a metal member beingplaced in said reel.
 9. The reel assembly according to claim 8, whereinsaid metal member comprises a metal tape fabricated by twisting metalwires into the form of a net.
 10. A method for winding an optical fibercomprising the steps of: winding an optical fiber on a reel with acontinuous outer circumference; and changing a length of the continuousouter circumference of the reel after winding.
 11. A reel assemblycomprising: a reel having a continuous outer circumference windingpotion, wherein a length of the continuous outer circumference windingportion being changeable after winding.
 12. The reel assembly of claim14 further comprising: a member, inside the winding portion, with anadjustable diameter, wherein adjusting the diameter changes the lengthof the continuous outer circumference winding portion.